Occludin (OCLN) gene exists on the long arm of human chromosome 5, and a protein encoded by this gene is a four transmembrane protein. OCLN forms a complex with a claudin family protein that is also a four transmembrane protein and constitutes a tight junction (J Cell Biol. 1998; 143(2): 391-401) and enhances electric resistance between cells by over-expression of OCLN in cells (J Cell Sci. 1996; 109: 2287-2298). As such, OCLN is considered to hold a role in the barrier function of tight junction. With regards to cancer, over-expression of OCLN in cells is reported to enhance the apoptosis signal and to suppress metastatic potential (Cancer Res. 2006; 66(18): 9125-9133).
Rho GTPase activating protein 26 (ARHGAP26) gene, which has GTPase activating function exists on the long arm of human chromosome 5, same as OCLN, and the protein encoded by this gene is a GTPase activating protein possessing a Rho-GAP domain at the center. ARHGAP26 gene is known to have a function to enhance the GTP hydrolase activity of the small GTPase protein family, particularly RhoA and CDC42 (J Biol Chem. 2000; 275(49): 38605-38610). With regards to cancer, a fusion gene with claudin 18 (CLDN18) gene was found in 3 to 15% of patients suffered from diffuse type gastric cancer (Nature 2014; 513(7517): 202-209, Cell Rep. 2015; 12(2): 272-285), and a fusion gene with a mixed-lineage leukemia (MLL) gene was found in leukemia patients (Proc Natl Acad Sci USA. 2000; 97(16): 9168-9173, Genes Chromosomes Cancer 2004; 41(4): 400-404).
There are no reports so far of a fusion gene composed of OCLN and ARHGAP26.